Barking machines of the above-mentioned type basically operate in such a manner that the individual log is fed lengthwise by means of rolls through the hollow space of an annular rotor on which a number of edgecarrying tools or swinging arms are hingedly mounted, at the same time as the rotor is caused to rotate, the tools and the cutting edges thereon being yieldably urged against the circumference of the log by means of suitable spring means enabling the cutting edges to follow any irregularities of the log surface. In these machines, logs of greatly varying thicknesses are worked, from slender stocks less than 100 mm in diameter to heavy saw timber with diameters in excess of 300 mm. In order to avoid that the swingable tools have to travel an unnecessarily long distance between the initial position which they assume during the periods between working of successive logs and the active position on the surface of a heavy log, the tools are adjustable in different initial positions by means of movable stops built into the rotor and limiting and determining the angle to which the spring means can swing the arms inwardly toward the center of the rotor, more particularly in such a manner that the tools in their initial positions are held swung-in with their cutting edges close to the center during working of an assortment of slender logs, whereas they are swung farther away from the center in the initial position for the working of thicker logs. In this manner, the tools need not climb an unnecesarily long distance over the log ends from the initial position to the active position during barking of heavy timber.
During operation, when the rotor of the machine rotates at maximum speed to give maximum barking capacity, the force by which the spring means strive to urge the tool cutting edges against the log circumference is counteracted by the centrifugal force exerted upon the tools by the rotation of the rotor. Naturally, the centrifugal force increases according as the rotor speed is increased. Furthermore, the pressure of the cutting edges upon the log is influenced by the positions of the centers of gravity of the tool arms relative to the associated pivot shafts, such that an increasing distance between the pivot shaft and the center of gravity exerts an increasing outwardly swinging torque on the swinging arms and thus a decreasing contact pressure of the cutting edges. In view hereof, if heavy logs are worked at high speeds, the contact pressure of the spring means may be counteracted to such an extent that the barking efficiency deteriorates.